In impact drill chucks the central rod is axially guided in the hollow drill spindle, and at least one coupling element is provided for connecting the drill chuck to the drill spindle. The coupling element can be arranged on the one hand in retainers of the drill spindle, and on the other hand in retainers in the chuck body of the drill chuck. As a function of its setting, the coupling element can allow an operating mode in which an axial play or displacement is permitted for the chuck body with respect to the drill spindle, and this axial play can be eliminated by way of a locking mechanism having a coupling ring.
The German patent publication DE-OS No. 34 13 581 (see the aforementioned applications as well) discloses a percussion drill in which the locking mechanism is a contact ring which is arranged on the drill spindle so that it can rotate or turn, but it is fixed when considered axially or longitudinally.
The contact ring is axially juxtaposed with an annular shoulder of the drill spindle, and it carries abutment or contact projections which are directed towards the annular shoulder. The abutment or contact projections preclude the axial shifting or displacement of the drill chuck on the drill spindle when they come into operative contact with the spindle's annular shoulder, i.e. the respective annular surface thereof.
The annular surface of the annular shoulder includes abutment recesses into which the abutment projections can extend, and the depth of these abutment recesses is at least equivalent to the magnitude of the permitted axial displacement or play of the drill chuck.
Accordingly, when the contact ring is turned such that the abutment projections are in alignment with the recesses and the projections can enter into the respective recesses, the axially directed shifting is set free, i.e. the axial displacement mode is available.
It follows that the drill spindle must be provided with abutment recesses which are adapted in size to the abutment projections of the chuck that is being used. Furthermore, the mentioned locking mechanism is primarily intended for such impact drills in which the axial displacement is of relatively minor magnitude, i.e. there is only a minor stroke or displacement distance.
However, when a chuck is to carry out a large stroke, for example, as large as that of the drill, in the mentioned locking mechanism the size (length) of the chuck is approximately increased in conformity with the distance of stroke of the attendant motion. Finally, in a percussion drill of the type described some inherently undesirable operational conditions may arise in that during the percussion operations with the mode with axial play the lock ring is not locked. Conversely, when the axial play mode is not used for normal drilling, the lock ring is locked, i.e. it can then not be used for clamping a drill.